The present invention relates generally to a signal transmission system implemented with optical fibers and related optical components. More particularly, this invention relates to a method and configuration for seamless adjustment and attachment in the process of making stable dual fiber optical components.
Fine tuning of optical components with angular movements of different parts for optical alignment is a time consuming and difficult task in the process of manufacturing and assembling the optical components comprise several optical parts. Furthermore, stability of attachment between these different parts after completion of the alignment operation is also required to assure long-term reliability to implement these optical components on optical fiber signal transmission systems. The difficulties often arise from the requirements of achieving a very secure attachment and meantime highly precise alignment. On the one hand, the alignment operation often affects the interface configuration between several parts, e.g., changes of the gap distance, angular orientations, etc. On the other hand, an operation of applying epoxy for attachment often changes the gap distance or even the angular orientations, thus degrading the precision of optical alignment. The degradation most come from the epoxy curing process and additionally, the thermal effect of epoxy layer is poor due to the poor thickness uniformity caused by the tilt orientation of the elements. The interference between these production processes adversely affects the environmental stability of a fiber optical component. Such problems are more pronounced for wavelength division multiplex (WDM) components manufactured with hybrid configurations combining different optical parts such as filters, collimators, fiber pigtails, etc. Particularly these components are now manufactured with reduced size while demand high alignment precision with stringent environmental stability requirements. Optical components manufactured with conventional technologies often cannot satisfy these requirements due to the limitations of existing assembly technologies.
One specific example is the dual fiber collimator commonly used in many different WDM fiber optic devices and hybrid components. The devices normally include a functional filter of thin film that is placed in front of a GRIN (gradient index) lens and a dual fiber capillary containing two optical fibers is placed behind the GRIN lens. There is no holding tube is used to hold these optical parts together since the capillary and the GRIN lens are not in the same line. The capillary needs to be adjusted in both position and angle to let a second fiber receive a reflected light beam incident from a first fiber by implementing a filter to reflect the light beam incident from the first optical fiber. The light transmitted to the first optical fiber passes through a GRIN lens to become a collimated beam with a portion of the beam reflected back to the second optical fiber by filter attached on the GRIN lens front surface and another portion transmitted through the filter. For the purpose of assembling such an optical component, epoxy is often applied throughout the optical surface between the GRIN lens and the capillary. The optical component is stable and highly reliable but the drawback is that the epoxy is spread onto the optical surface that may cause some problems of degradation of epoxy exposure under laser for long time. Another technology is to apply epoxy into partial area between the GRIN lens and the glass capillary to prevent the epoxy spreading over the optical paths. However, such components are less environmentally stable and problems associated with structure degradation may occur to adversely affect the reliability and performance of operation. Many attempts were made to solve the problem, one method is to firmly fix the GRIN lens and capillary in tube, then adjust the orientation of the filter. After the adjustment finished, epoxy is applied to fix the filter on the GRIN lens surface. The components made in such method are not stable also because the epoxy layer is not uniform due to the filter being tilted. In this invention, a method is disclosed to firmly fix the filter before the GRIN lens with uniform and tiny gap.
Therefore, a need still exits in the art of design and manufacture of fiber optical components assembled with several optical elements such as filter and collimator to provide new configurations and method of manufacturing and assembling methods such that these difficulties can be resolved. Preferably, the new configuration and method of manufacturing can be applied to enhance and improve current manufacturing processes to achieve higher production quality and meanwhile achieve lower production cost of optical components.
It is therefore an object of the present invention to provide an improved configuration and method for manufacturing the optical components by providing angular freedom of movement at the interface between optical parts to seamlessly and continuously perform orientation adjustment such that above difficulties and problems are resolved.
Specifically, it is an object of the present invention to provide an improved configuration and method for manufacturing the optical component by providing spherical tube end interface configuration to allow for angular movement freedom and to provide sufficient areas of attachment by applying the epoxy. The new and improved configuration and method enhance the manufacture process and provide stable attachment between the interface surface areas such that the optical components are made with long-term structure reliability. The epoxy is prevented from spreading over the optical path because the surface tension between the epoxy and the surface are of the tube ends keep the epoxy from entering into the inner parts of the holding tubes.
Briefly, in a preferred embodiment, the present invention includes a dual fiber optical component that includes a first holding tube for containing and holding a dual fiber capillary and a collimator lens. The dual fiber capillary has first optical fiber and a second optical fiber with the first optical fiber receives an input light beam for projecting through the collimating lens as a collimated beam. The dual fiber component further includes a second holding tube containing and holding an optical filter for receiving the collimated beam from the collimating lens. The filter further reflects a portion of the collimated beam back through the collimator lens to transmit to the second optical fiber of the dual-fiber capillary. The first holding tube has a first interface tube end forming with a convex spherical profile and the second holding tube has a second interface tube end forming with a concave spherical profile corresponding to the convex spherical profile of the first interface tube end. The first interface tube-end and the second interface tube-end can seamless fit together to have a multiple dimensional freedom of angular movement for adjusting a relative orientation of the first holding tube to the second holding tube.
In summary, this invention discloses a method of manufacturing and assembling an optical component comprising at least a first and a second optical element. The method includes a step of providing a first interface nonlinear profile for a first optical part. The method further includes a step of providing a second non-linear profile for the second optical component. The second non-linear interface profile is conjugated to the first non-linear interface profile such that the first optical element and the second optical element can seamlessly fit together and having a multiple dimensional freedom of angular movement relative to each other.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment, which is illustrated in the various drawing figures.